Level detector for a material in a container

ABSTRACT

A level detector includes a rod probe for positioning at least partially within a container suitable for containing a material. The rod probe has first and second ends. A monitoring device is coupled with the first end of the rod probe. The monitoring device is operable to produce a reading when a ground connector contacts the monitoring device. The reading is based upon whether the second end of the rod probe contacts the material. The reading may also be based upon an electrical impedance of the material when the second end of the rod probe contacts the material.

TECHNICAL FIELD OF THE INVENTION

[0001] This invention relates to measurement devices, and moreparticularly to a level detector for measuring the level of a materialin a container.

BACKGROUND OF THE INVENTION

[0002] Level detection is used in a vast number of applications. Highlevel detectors have special importance for a number of economic andsafety reasons. For example, domestic liquid-propane (“LP”) gas tanksshould not be filled above ninety percent of tank capacity, because heatcan raise the pressure inside the tank to dangerous levels.

[0003] When filling an LP gas tank, an operator opens a valve at the topof the tank and fills the tank until the valve emits gas in liquid form.This is because the valve is connected to a tube with such a length thatonly liquid gas can be released when ninety percent of capacity isreached. This process can send polluting gas into the atmosphere therebyendangering the operators and anyone else nearby.

[0004] Level detection within tanks of fuels like gasoline oil andliquefied gas can be difficult using electric properties of these fuelsbecause of their high electrical impedance. Furthermore, float sensorsare difficult to use because of the erratic movement of the wavesgenerated while filling the tank with these materials.

SUMMARY OF THE INVENTION

[0005] The present invention provides a level detector and method oflevel detection for materials contained in tanks that substantiallyeliminates or reduces at least some of the disadvantages and problemsassociated with the previous level detectors and methods.

[0006] In accordance with a particular embodiment of the presentinvention, a level detector is provided. The level detector includes arod probe for positioning at least partially within a container suitablefor containing a material. The rod probe has first and second ends. Amonitoring device is coupled with the first end of the rod probe. Themonitoring device is operable to produce a reading when a groundconnector contacts the monitoring device. The reading is based uponwhether the second end of the rod probe contacts the material. Thereading may also be based upon an electrical impedance of the materialwhen the second end of the rod probe contacts the material. The groundconnector may be a person.

[0007] In accordance with another embodiment, a level detector isprovided. The level detector includes a rod probe for positioning atleast partially within a container suitable for containing a material.The rod probe has first and second ends. A monitoring device is coupledwith the first end of the rod probe. The monitoring device includes atleast part of a circuit. The circuit has a frequency. The monitoringdevice is operable to produce a reading when a ground connector contactsthe monitoring device. The reading is related to the frequency of thecircuit. The frequency may be related to an electrical impedance of thecircuit.

[0008] Technical advantages of particular embodiments of the presentinvention include a level detector that displays a reading enabling auser to determine when a material is filled to a particular level withina container. Accordingly, overfilling the container to determine whenthe container is full of the material is unnecessary.

[0009] Another technical advantage of particular embodiments of thepresent invention includes a level detector that produces a frequencybased upon the electrical impedance of the material in the container.Accordingly, a user can determine the type of material in the containerbased upon the frequency produced by the level detector. Furthermore, auser may be able to determine if there are contaminant materials in thecontainer.

[0010] Another technical advantage of particular embodiments of thepresent invention includes a level detector which uses a rod probepositioned partially within the container to detect the level of thematerial in the container. Accordingly, installation is less difficultand does not require a wide orifice as a float sensor may require.

[0011] Another technical advantage of particular embodiments of thepreset invention includes a level detector with a circuit that uses aperson as a ground connection to begin current flow through the circuit.Accordingly, less components are needed to operate the level detector.

[0012] Other technical advantages will be readily apparent to oneskilled in the art from the following figures, descriptions and claims.Moreover, while specific advantages have been enumerated above, variousembodiments may include all, some or none of the enumerated advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] For a more complete understanding of particular embodiments ofthe invention and their advantages, reference is now made to thefollowing descriptions, taken in conjunction with the accompanyingdrawings, in which:

[0014]FIG. 1 is a diagram illustrating a level detector and a tank inaccordance with an embodiment of the present invention; and

[0015]FIG. 2 is schematic diagram illustrating a circuit of a leveldetector in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0016]FIG. 1 illustrates a level detector 10 in accordance with aparticular embodiment of the present invention. Level detector 10includes a rod probe 12 positioned at least partially within a tank 14.Rod probe 12 has a first end 26 connected to a monitoring device 24 anda second end 28 disposed within tank 14. Rod probe 12 is positionedthrough a grommet 20 at an opening 22 of tank 14. Tank 14 contains amaterial 16 having a top surface 18 inside tank 14. Material 16 may be afluid, such as gasoline oil or LP gas, or any other material suitable tobe contained in a container. Monitoring device 24 is coupled with firstend 26 of rod probe 14. Monitoring device 24 includes part of a circuit32.

[0017] When a ground connector 30 contacts monitoring device 24, groundconnector 30 provides a ground connection for circuit 32. In theillustrated embodiment, ground connector 30 is a person; however, inother embodiments ground connector 30 may comprise any suitableapparatus sufficient to establish a ground connection for circuit 32.When such ground connection is established, an electric path iscompleted between ground connector 30, monitoring device 24 and rodprobe 12; and thus, current flows through circuit 32.

[0018] Upon the completion of the electric path, monitoring device 24produces a reading. The characteristics of the reading depend on whethersecond end 28 of rod probe 12 is in contact with material 16. If secondend 28 of rod probe 12 is in contact with material 16, thecharacteristics of the reading produced by monitoring device 24 may varydepending on what type of material 16 is contained in tank 14. Leveldetector 10 enables a user to determine whether top surface 18 ofmaterial 16 is at a particular height level in tank 14. A user can makethis determination by viewing the characteristics of the readingproduced by monitoring device 24, as discussed in greater detail below.

[0019] In the illustrated embodiment, rod probe 12 comprises a metalmaterial; however, rod probe 12 may comprise any other suitableconducting material. The size, shape and configuration of rod probe 12may vary. A user of level detector 10 may choose a particular heightlevel within tank 14 as a reference level in determining the level oftop surface 18 of material 16. In the illustrated embodiment, suchreference level is labeled as 36; however, the reference level chosen bythe user may be any level within tank 14.

[0020] The user positions rod probe 12 so that second end 28 is at orbelow reference level 36 within tank 14. If top surface 18 of material16 is at or above reference level 36, then second end 28 will contactmaterial 16. Such contact will enable a user to determine when topsurface 18 is at or above reference level 36 based on the readingproduced by monitoring device 24 when a ground connector is in contactwith monitoring device 24. In the illustrated embodiment, the user oflevel detector 10 may act as ground connector 30.

[0021] Tank 14 is made of a metal alloy; however, in other embodimentstank 14 may be made of any other suitable material. Grommet 20 coupledto tank 14 provides isolation for circuit 32. Such isolation preventscircuit 32 from shorting out as a result of contact between rod probe 12and tank 14 for embodiments where tank 14 includes a conductivematerial.

[0022] As stated above, monitoring device 24 contains part of circuit 32and produces a reading. In the illustrated embodiment, circuit 32 is aresistance-capacitance (“RC”) oscillator circuit which produces anoscillating frequency when the electric path is created between groundconnector 30, monitoring device 24 and rod probe 12.

[0023] Circuit 32 includes a light-emitting diode (“LED”) 40 thatdisplays the reading produced by monitoring device 24. The reading isdisplayed by the blinking of LED 40 at the oscillating frequencyproduced by circuit 32. Other embodiments of the present invention mayprovide for other ways to display the reading. For example, in analternative embodiment a numerical LED may be used to display thereading produced by monitoring device 24. Furthermore, alternativedisplays other than LEDs may be used.

[0024] When current flows through circuit 32, circuit 32 has a certainelectrical impedance, or opposition to current flow. If second end 28 ofrod probe 12 contacts material 16 in tank 14, the electrical impedanceof circuit 32 changes. This is because material 16 has its ownelectrical impedance which affects the electrical impedance of circuit32. The change in electrical impedance of circuit 32 changes theoscillating frequency produced by circuit 32, resulting in a change inthe frequency at which LED 40 blinks. Thus, a user of level detector 10can determine whether second end 28 is in contact with material 16 byobserving the frequency at which LED 40 is blinking.

[0025] For example, a user may observe LED 40 blinking at a particularfrequency when the tank 14 is empty and the electric path is created.Rod probe 12 may be positioned partially within tank 14 so that secondend 28 is at reference level 36 within tank 14. Then, material 16 may beadded to tank 14. When top surface 18 of material 16 is at or abovereference level 36, then material 16 will be in contact with second end28. At this time, the frequency at which LED 60 is blinking will change.This change will let the user know that tank 14 is filled to referencelevel 36 with material 16.

[0026] Different materials contained in tank 14 affect the electricalimpedance of circuit 32 in different ways. Thus, a user may also be ableto identify what material is contained in tank 14 according to theparticular frequency at which LED 40 is blinking. Moreover, a user maybe able to determine if there are contaminant materials within tank 14.For example, in one embodiment of the present invention, liquid-propane(“LP”) gas gives a frequency of approximately two hertz. In anotherembodiment, bond paper gives a frequency of approximately twenty hertz.Various other materials may be contained in tank 14, giving off varyingfrequencies.

[0027]FIG. 2 is a schematic diagram illustrating certain components of alevel detector 50 in accordance with another embodiment of the presentinvention. Level detector 50 includes rod probe 52 positioned partiallywithin tank 54. Rod probe 52 has a first end 57 and a second end 58.Second end 58 is disposed within tank 54. Tank 54 contains a material 56having a top surface 60. Rod probe 52 is positioned through grommet 62which is coupled to tank 54 at an opening 63 of tank 54.

[0028] First end 57 of rod probe 52 is connected to a monitoring device64. Monitoring device 64 contains part of a circuit 65. In theillustrated embodiment, circuit 65 includes an oscillator 66, a groundconnector 67, an isolator 70, an amplifier 75, an LED 82 and a powersource 86. Monitoring device 64 also contains part of oscillator 66.Oscillator 66 comprises capacitors 68, rod probe 52 and material 56. Inthe illustrated embodiment, oscillator 66 includes three capacitors 68,but other embodiments may include one, two or more than threecapacitors. Capacitors 68 diminish the current loss through circuit 65.Capacitors 68 are of a low-leakage type.

[0029] Monitoring device 64 also contains isolator 70. Isolator 70 aidsin isolation between oscillator 66 and amplifier 74 which is discussedbelow when current flows through circuit 65. In the illustratedembodiment, isolator 70 includes three Schmidt trigger CMOS gates.However, other embodiments may have isolators that include other typesof components.

[0030] Monitoring device 64 also includes amplifier 74. Amplifier 74includes resistors 76, 78 and 80. Resistors 76 and 78 perform currentamplification, and resistor 80 sets the current for LED 82. Capacitor 84eliminates the need for a power switch to activate LED 82. Power source86 provides power to circuit 65.

[0031] Ground connector 67 provides a connection to ground for circuit65 when ground connector 67 contacts monitoring device 64. Groundconnector 67 may be a person or any suitable apparatus sufficient toestablish a connection to ground for circuit 65. When a connection toground is established, current flows through circuit 65.

[0032] LED 82 blinks at the frequency produced by oscillator 66. Ifsecond end 58 of rod probe 52 contacts material 56, then the electricalimpedance of oscillator 66 is affected, and the frequency at which LED82 blinks changes. By observing this change, a user of level detector 50can determine when top surface 60 of material is at or above thereference level of second end 58. By observing such frequency, a usermay also be able to determine the type of material in contact withsecond end 58 of rod probe 52.

[0033] Although the present invention has been described in detail,various changes and modifications may be suggested to one skilled in theart. It is intended that the present invention encompass such changesand modifications as falling within the scope of the appended claims.

What is claimed is:
 1. A level detector, comprising: a rod probe for positioning at least partially within a container suitable for containing a material, the rod probe having first and second ends; a monitoring device coupled with the first end of the rod probe; wherein the monitoring device is operable to produce a reading when a ground connector contacts the monitoring device; and wherein the reading is based upon whether the second end of the rod probe contacts the material. 2 The level detector of claim 1, wherein the reading is based upon an electrical impedance of the material when the second end of the rod probe contacts the material.
 3. The level detector of claim 1, wherein the ground connector is a person.
 4. The level detector of claim 1, wherein the rod probe is positioned within an isolation grommet; and wherein the isolation grommet is coupled to the container at an opening of the container.
 5. The level detector of claim 1, wherein the monitoring device comprises a light-emitting diode (LED) operable to display the reading.
 6. The level detector of claim 1, wherein the monitoring device comprises at least part of an oscillation circuit.
 7. The level detector of claim 1, wherein the material is liquid-propane gas.
 8. A level detector, comprising: a rod probe for positioning at least partially within a container suitable for containing a material, the rod probe having first and second ends; a monitoring device coupled with the first end of the rod probe, the monitoring device comprising at least part of a circuit, wherein the circuit has a frequency; wherein the monitoring device is operable to produce a reading when a ground connector contacts the monitoring device; and wherein the reading is related to the frequency of the circuit.
 9. The level detector of claim 8, wherein the frequency is related to an electrical impedance of the circuit.
 10. The level detector of claim 9, wherein the electrical impedance of the circuit changes when the second end of the rod probe contacts the material.
 11. The level detector of claim 8, wherein the circuit comprises an oscillator.
 12. The level detector of claim 8, wherein the circuit comprises an isolator.
 13. The level detector of claim 8, wherein the circuit comprises an amplifier.
 14. The level detector of claim 8, further comprising a light-emitting diode (LED) operable to display the reading.
 15. The level detector of claim 8, wherein the material is liquid-propane gas.
 16. The level detector of claim 8, wherein the ground connector is a person.
 17. A method for detecting a level of a material in a container, comprising: positioning a rod probe at least partially within a container, the rod probe having first and second ends; connecting a monitoring device to the first end of the rod probe, the monitoring device operable to produce a reading when a ground connector contacts the monitoring device; contacting the monitoring device with a ground connector; and wherein the reading is based upon whether the second end of the rod probe contacts a material.
 18. The method of claim 17, wherein the reading is based upon the electrical impedance of the material when the second end of the rod probe contacts the material.
 19. The method of claim 17, wherein the ground connector is a person.
 20. The method of claim 17, wherein the material is liquid-propane gas.
 21. The method of claim 17, wherein the monitoring device comprises at least part of a circuit.
 22. The method of claim 21, wherein: the circuit has a frequency; and the reading is related to the frequency of the circuit.
 23. The method of claim 22, wherein the frequency is related to an electrical impedance of the circuit.
 24. The method of claim 23, wherein the electrical impedance of the circuit changes when the second end of the rod probe contacts the material. 